<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <header>
        <%
            if(isLogin){
                %>
                    <span>欢迎回来</span>
                <%
            }else{
                %>
                <button>登录</button>
                <%
            }
        %>
    </header>
</body>
</html>